The invention relates generally to the field of power line networking technologies. Further, the invention relates to a signal interface between a computer""s power supply line and a computer""s data communications interface.
Power line technology (PLT) has been and will continue to be introduced to the consumer market at a fast pace to support in home networking or other local network situations. For example, multiple computers in the home may be networked together by utilizing the home""s power line circuitry to carry data communication signals at a frequency different from the frequency at which power is transmitted. Further, other data processing devices may be networked in the home in a similar manner. For example, appliance devices in the home may be networked using power line technology as well as in home communication devices, such as telephones, video devices, home security devices, monitoring devices, etc.
Conventionally, personal computers (PCs) are not necessarily optimized to support PLT. Currently, a basic architecture of an add-on PLT system is either an internal PC card (e.g., ISA or PCI), that the user installs in an existing computer, or an external stand-alone box with a USB or parallel cable interfaced to the PC. The PLT module, whether it be internal or external, must be coupled in some manner to the power line. Generally, the PLT module is coupled to the power line by plugging a signal coupler module into an empty power outlet in the vicinity of the personal computer. In order to accomplish this coupling, the existence of an empty power outlet is needed, which is rarely the case in the vicinity of a personal computer system, because monitors, printers, and other accessories are normally present and connected to a power strip. In the case that an empty outlet is available, the user is forced to couple the PLT module to a relatively noisy power node, where the PC is directly connected, without adequate filtering. Coupling the PLT module to a noisy power node has the potential to affect operation and performance of the PLT network, depending on the type of power supply used for the PC and any accessories connected to it.
In the case that a power strip is being used, conventional power strips may contain filters, which effectively decouple high-frequency signals from the power line. Therefore, it is not necessarily appropriate to couple a PLT adapter to the power strip for optimum performance, because some of the high-frequency signals, which the power strip may filter out, may be needed for proper PLT home networking communication. Even if the power strip does not contain filters, it is not appropriate to couple a PLT module to the power strip or to an outlet in its vicinity because of the excessive noise and low impedance presented by the PC power supply and all its peripherals connected to the strip.
In a typical PLT networking interface, a transformer interface is used to couple the high-frequency data carrier signal to the power line. The transformer""s primary winding is connected to the alternating current (AC) outlet of the power line through a coupling capacitor. The transformer""s secondary winding is connected to a data carrier signal driver/receiver within the PC or the PLT module. The transformer isolates the PC system from the power line and at the same time rejects AC electrical power signal component. Furthermore, the transformer is coupled to the power line by a physical connector other than the PC power cable, to avoid any interference caused by the PC switching power supply.
Prior coupling technology is generally rudimentary, as an external port needs to be provided on a PC to support the connection of the data carrier signal to the power line, when the PC is already connected to the power line through the PC power cord. Further, a complete, self-contained interconnection module is required from the PC to the AC power outlet to provide the necessary coupling function. Thus, substantial expense for PLT networking devices lies in the redundancy of connections to the power line network, where the PC is already connected.
Referring to FIG. 1, a personal computer (PC) 10 of the prior art is depicted. PC 10 includes, among other hardware, a PC power supply 15. PC power supply 15 conventionally includes a power cord 20 including an AC plug 25, for coupling to a conventional power receptacle. In an exemplary embodiment, AC plug 25 may be, but is not limited to a J-type plug. In a typical implementation, an electromagnetic interference (EMI) filter 25 is coupled between power cord 20 and PC power supply 15. A conventional EMI filter 25 includes a capacitor 30 coupled across the hot (H) and neutral (N) terminals of AC plug 25. A transformer 35 is coupled between the H and N terminals and to the capacitors 40 and 45 coupled between the H terminal and ground and between the N terminal and ground respectively. Power line EMI filter 25 is typically present in most switching power supplies. Transformer 35 is commonly implemented as two common mode choke (same toroid) inductors in series with the power supply terminals 50 and 55. The two inductors are wound on a common toroid, and their purpose is to suppress EMI emission from the internal power supply circuitry by de-coupling high-frequency noise from the power line (inductors typically present high impedance to high-frequency). In a conventional implementation, the value of such inductors is on the order of one milliHenry (mH). In a conventional implementation capacitor 30 which may be on the order of 0.1 microFarads (uF) may or may not be added across H and N to further de-couple noise injected to the power through the PC power cord.
Accordingly, there is a need for a PLT networking device that couples the signal driver/receiver within the PC to the power line without an external port, power/signal line, and/or interconnection module. Further, there is an alternative need for a PLT adapter for retrofitting existing PCs, having a PLT analog front end (AFE) card, the PLT adapter including data signal input, a power line input and a power output for coupling to the PC power supply. Further, there is another alternative need for a power strip that is optimized for PLT home networking. The power strip includes a power filter built into the power strip with a PLT coupler.
An exemplary embodiment of the invention relates to an apparatus for carrying electrical data signals and electrical power over a power line. The apparatus includes a data processing device, power supply, and a data signal transceiver. Further, the apparatus includes an interference filter coupled to the power line and to the power supply and configured to reject electromagnetic interference. Further still, the apparatus includes a coupling circuit electromagnetically coupled to the power line. The coupling circuit is configured to transmit and receive data signals carried through the power line. The coupling circuit is also coupled to the data signal transceiver. The data signal transceiver is configured to transmit and receive the data signals to and from the data processing device.
Another exemplary embodiment of the invention relates to a power strip configured for power line networking. The power strip includes an electrical plug. The power strip also includes a power filter for rejecting electromagnetic interference. The power filter is coupled to the electrical plug. The power strip further includes an inductor coupled to the power filter and coupled to a signal coupling. Further still, the power strip includes a power outlet coupled to the power filter.
Yet another exemplary embodiment of the invention relates to a power line networking adapter. The power line networking adapter includes a power line coupling input. The power line networking adapter also includes an interference filter coupled to the power line coupling input. Further, the power line networking adapter includes an electromagnetic circuit coupled to the filter circuit. Further still, the power line networking adapter includes a data signal connector coupled to the electromagnetic circuit.
Still yet another exemplary embodiment of the invention relates to a method of coupling a data processing device to a power line, the power line carrying electrical power and a data signal. The method includes coupling a power supply for the data processing device to the power line through an interference filter, the interference filter is configured to reject electromagnetic interference. The method also includes electromagnetically coupling a data signal carrier from a data signal transceiver to the power line to provide an electromagnetic coupling circuit. The electromagnetic coupling circuit is configured to transmit and receive the data signal being carried over the power line